In this paper, we examine the effects of the global rating recalibration conducted by Moody's and Fitch credit rating agencies in early 2010. We test the hypothesis forwarded by the rating agencies that the recalibration was “yield neutral.” Using time series methods, we find that the rating recalibration brought a structural change to the municipal bond market and increased the spread of municipal bonds in the Aaa, Aa, and A rating categories over their risk-free comparison group by approximately 15 basis points. The impact of the rating recalibration on the spread of Baa-rated bonds was not statistically significant. © 2017 Public Financial Publications, Inc.